Macro define_histogram 

macro_rules! define_histogram {
    ($name:ident < $label:ty > = $buckets:expr) => { ... };
}

Defines a histogram type with compile-time validated bucket boundaries.

This macro creates a newtype wrapper around Histogram<L, N> with specific bucket boundaries. The bucket values are validated at compile time to ensure they are in strictly ascending order.

Syntax

define_histogram!(HistogramName<LabelType> = [bucket1, bucket2, ...]);

Examples

Define a histogram with custom labels:

use aetos::{define_histogram, Label};

#[derive(Label, Hash, Eq, PartialEq, Clone, Debug)]
struct HttpLabel {
    method: &'static str,
    status: u16,
}

define_histogram!(HttpLatency<HttpLabel> = [0.05, 0.1, 0.5, 1.0, 5.0]);

Define an unlabeled histogram:

use aetos::define_histogram;

define_histogram!(ResponseTime<()> = [0.1, 0.5, 1.0]);

Invalid bucket ordering fails at compile time:

use aetos::define_histogram;

// This will fail because buckets are not in ascending order
define_histogram!(Bad<()> = [1.0, 0.5, 2.0]);

Histogram labels come from the type parameter, not the label attribute:

use aetos::{define_histogram, metrics};

define_histogram!(ResponseTime<()> = [0.1, 0.5, 1.0]);

#[metrics]
struct Metrics {
    // This will fail - histograms don't support 'label' attribute
    #[histogram(help = "Response time", label = "endpoint")]
    response_time: ResponseTime,
}